本文關(guān)鍵詞：單晶鈮酸鋰薄膜的結(jié)構(gòu)和屬性研究　出處：《山東大學(xué)》2016年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 離子注入 LNOI 損傷 鈮酸鋰 近化學(xué)計(jì)量比 微環(huán)

【摘要】：從20世紀(jì)末開始集成光學(xué)得到了迅速的發(fā)展,它可以實(shí)現(xiàn)將多個(gè)光學(xué)元件集成在同一塊芯片材料上,形成一個(gè)結(jié)構(gòu)復(fù)雜、功能強(qiáng)大的微型/小型器件,以實(shí)現(xiàn)一種或多種光學(xué)功能,在傳感、通信/信號(hào)傳輸、環(huán)境檢測等領(lǐng)域都有廣泛的應(yīng)用。集成光學(xué)在現(xiàn)代光通信和光信息處理應(yīng)用中起了不可替代的作用,而薄膜則是集成光學(xué)系統(tǒng)一個(gè)關(guān)鍵的組成部分。將具有不同光學(xué)性質(zhì)的單晶材料通過一定方式結(jié)合在一起形成薄膜材料,可以實(shí)現(xiàn)單一晶體所無法實(shí)現(xiàn)的功能。鈮酸鋰(LiNbO3, LN)晶體是集成光學(xué)應(yīng)用最多的一種晶體材料,因?yàn)槠渥陨砭哂卸喾N優(yōu)良的光學(xué)性能,如壓電、鐵電、光電、光彈、熱釋電、光折變和非線性等光學(xué)性質(zhì)。LN晶體有光學(xué)“硅”材料之稱,成為少數(shù)經(jīng)久不衰、源源不斷開辟應(yīng)用新領(lǐng)域的光學(xué)功能材料。近十幾年以來,出現(xiàn)了一種制作高折射率差單晶薄膜的方法。離子注入技術(shù)和晶體鍵合技術(shù)相結(jié)合,將單晶鈮酸鋰薄膜鍵合到沉積有SiO2(也可以是別的材料)的絕緣體襯底,制備出單晶鈮酸鋰薄膜(lithium niobate on insulator, LNOI)。本論文中用的LNOI材料是三明治結(jié)構(gòu)：LN薄膜/SiO2層/LN襯底。最上面是一層LN薄膜,厚度大約0.5μm,中間一層是非晶的SiO2,厚度約2μm,最下面一層是LN襯底。LN薄膜和SiO2層形成的高折射率差對光形成限制作用。光被限制在一個(gè)很小的空間內(nèi),在很低的入射能量下,LNOI制作的波導(dǎo)中光的能量密度就可以達(dá)到很高的量級(jí)。LN體材料中的某些光學(xué)性質(zhì),例如非線性光學(xué)效應(yīng)和電光效應(yīng),在LNOI中可以得到一定程度的加強(qiáng)。LNOI作為一種制作集成光學(xué)器件的理想平臺(tái),制作的光學(xué)器件的性能可能有大幅度的提高,迄今已經(jīng)有不少在LNOI上制作的器件的報(bào)道。但是器件的性能在很大程度上取決于材料的性能,所我們所知,關(guān)于LNOI光學(xué)和結(jié)構(gòu)屬性的報(bào)道并不多。因此,對于LNOI的結(jié)構(gòu)和光學(xué)屬性應(yīng)該進(jìn)一步的探討,這對于設(shè)計(jì)、制備、評(píng)價(jià)LNOI上的集成光學(xué)器件有幫助和推動(dòng)作用。LNOI樣品制備中用到的核心技術(shù)之一是離子注入。離子注入過的光學(xué)晶體在應(yīng)用上還存在著一些困難和挑戰(zhàn),關(guān)于離子注入的材料物理性質(zhì)的研究和認(rèn)識(shí)的缺乏是限制LNOI應(yīng)用的主要原因之一,其中因?yàn)殡x子注入引起的缺陷和損傷的性質(zhì)是至關(guān)重要的。一般認(rèn)為在離子注入的過程中,注入離子與靶中的電子和晶格原子發(fā)生碰撞等相互作用,對晶格結(jié)構(gòu)有一定程度的破壞。離子注入引起的晶體損傷會(huì)降低LN的電光系數(shù)、二階非線性系數(shù)等光學(xué)性質(zhì)。論文研究了LNOI中的晶格結(jié)構(gòu),測量了LNOI的平行方向和垂直方向的應(yīng)力和LN薄膜層與襯底層在晶面上的取向差,基于棱鏡耦合技術(shù)測量了線性電光系數(shù)γ13和γ33,在LNOI上制備了微環(huán)諧振器,還提出了近化學(xué)計(jì)量比LN薄膜的制作方法。本論文研究的主要內(nèi)容與結(jié)果如下：1.LNOI晶格結(jié)構(gòu)的研究在LNOI制作過程中離子注入過程能導(dǎo)致晶格損傷,在論文中我們通過在氧氣的氣氛下退火來恢復(fù)晶格結(jié)構(gòu)。實(shí)驗(yàn)中使用棱鏡耦合技術(shù)、盧瑟福背散射／溝道技術(shù)、共聚焦微拉曼散射和高分辨透射電鏡來研究在不同退火條件下LNOI的晶格損傷,用高分辨X射線評(píng)估LNOI的晶格結(jié)構(gòu)。實(shí)驗(yàn)證明在氧氣的環(huán)境中經(jīng)過520℃下5個(gè)小時(shí)的退火,離子注入的損傷得到了很大程度的恢復(fù)。LNOI的雙折射接近于體材料；溝道譜中顯示在近表面LNOI是一個(gè)完美晶體；拉曼譜中顯示LNOI和LN體材料的譜線幾乎吻合；透射電鏡橫截面圖中顯示在LiNbO3薄膜/Si02層界面上僅僅有一層非常薄的非晶過渡層,其余區(qū)域晶格條紋清晰；選區(qū)電子衍射的圖中沒有出現(xiàn)非晶環(huán),并且衍射圖案是六邊形格子圖案,高分辨X射線顯示LNOI很好的晶格排列。2.LNOI應(yīng)力的研究在影響薄膜材料的諸多因素中,應(yīng)力是不可能忽視的一個(gè)重要因素。應(yīng)力的存在會(huì)直接影響薄膜材料的穩(wěn)定性和可靠性,嚴(yán)重的情況下可能會(huì)造成薄膜的脫落。LNOI的結(jié)構(gòu)雖然只有幾百納米的厚度,但是應(yīng)力的存在能導(dǎo)致界面的晶格扭曲,從而影響薄膜的光學(xué)性能和電學(xué)性能,還可能誘導(dǎo)不可預(yù)知的破壞力影響器件性能。LNOI應(yīng)力的研究對于光學(xué)器件的制備非常重要。高分辨X射線(HRXRD)的ω-20掃描可以用來表征LNOI的平行和垂直方向的應(yīng)力,因?yàn)閤-ray表征的時(shí)候是無損的,而且具有高精度和很強(qiáng)的穿透力。HRXRD從LN薄膜層中得到的圖像提供了直接測量薄膜應(yīng)變分量的一種辦法。根據(jù)薄膜峰的位置變化計(jì)算得出晶格常數(shù),再用晶格常數(shù)表征應(yīng)力,包括垂直方向的壓力和平行方向的拉力。HRXRD的φ掃描還可以測出在某個(gè)晶面上LN薄膜層和襯底在鍵合過程對齊時(shí)的取向差(δφ)。由于LN薄膜和SiO2層的熱膨脹系數(shù)不同,形成了LN薄膜的垂直方向和水平方向的應(yīng)變分量。實(shí)驗(yàn)結(jié)構(gòu)表明,由于LN薄膜的熱膨脹系數(shù)遠(yuǎn)大于Si02,退火后晶格常數(shù)水平方向a,變大,垂直方向cr變小。HRXRD的φ掃描探測的在(104)上LN薄膜層和襯底的取向差是0.98°3.LNOI線性電光系數(shù)的研究LN晶體有優(yōu)良的電光特性,具有較大電光線性系數(shù)(γ13=9.5 pm/V,γ33=31.2pm/V)。LN晶體作為集成光學(xué)系統(tǒng)的基礎(chǔ)部分,被用來實(shí)現(xiàn)許多光學(xué)器件,包括聲光器件、表面濾波器、電光開關(guān)、電光調(diào)制器等。對于LNOI來說,希望LN薄膜層跟體材料一樣,也具有較大的電光系數(shù)。離子注入導(dǎo)致的晶格損傷,可能會(huì)影響到LN薄膜層電光系數(shù)。論文中改進(jìn)了一種基于棱鏡耦合技術(shù)的平面波導(dǎo)電光系數(shù)的測量方法。使用棱鏡耦合技術(shù)測量出LNOI的折射率,通過上下電極加上電場后,再測量調(diào)制后折射率,通過折射率的變化來確定LNOI的線性電光系數(shù)。利用此方法在入射光波長是632.8 nm的時(shí)候測量了LNOI的電光系數(shù)γ13和γ33。結(jié)果顯示,在氧氣的氣氛下,經(jīng)過520℃/5h退火處理的LNOI的線性電光系數(shù)γ13和γ33和LN體材料的很接近。4. LNOI上微環(huán)諧振腔的研究在LNOI上面制備的光學(xué)器件,將會(huì)大幅度提高基于非線性效應(yīng)的光學(xué)性能。由環(huán)形的光波導(dǎo)和直的光波導(dǎo)耦合而成的微環(huán)諧振器是一個(gè)結(jié)構(gòu)緊湊的光學(xué)濾波器,它可以用來構(gòu)建多種不同用途的集成光學(xué)器件,包括光調(diào)制器、光開關(guān)、光插分復(fù)用器、光路由器、光傳感器等。論文中在LNOI上面設(shè)計(jì)了微環(huán)諧振腔。將樣品拋光成楔形,微環(huán)諧振腔刻蝕在楔形樣品的尖上,實(shí)現(xiàn)了聚焦離子束刻蝕時(shí)不用換視野,大大提高了刻蝕的精度。我們搭建了LNOI微環(huán)諧振腔與單模光纖的耦合系統(tǒng)。有關(guān)微環(huán)諧振器與直波導(dǎo)耦合效果的測試工作正在進(jìn)行中。5.近化學(xué)計(jì)量比LiNbO3薄膜的制備和表征LN晶體是一種典型的非化學(xué)計(jì)量比1：1的晶體,商業(yè)用的LN晶體具有同成分的配比([Li]/[Nb]=48.4/51.6)。鋰離子的缺失造成晶體中存在大量的空位缺陷,致使LN晶體的許多物理性能受到一定的影響。LNOI是從LN晶體上剝離下來的,成分也不例外。近化學(xué)計(jì)量比的LN晶體已經(jīng)出現(xiàn),其中一些物理屬性得到了的改變,如反轉(zhuǎn)電壓明顯降低、雙折射差增大等。因此很有必要制作高品質(zhì)的近化學(xué)計(jì)量比的LN薄膜,探索折射率差、晶格常數(shù)和偶極矩等物理性質(zhì)。論文中采用富鋰氣相傳輸平衡技術(shù)在氧氣的氣氛下520℃退火5小時(shí)提高LNOI中的Li/Nb比,制備近近化學(xué)計(jì)量比鈮酸鋰薄膜(NSLNOI)。使用棱鏡耦合儀測量折射率,在激光波長632.8 nm時(shí)測得NSLNOI異常光的折射率是2.1983,小于同成分LN的2.2024,向化學(xué)計(jì)量比LN的2.1898靠近。使用高分辨X射線的的ω-20掃描測得NSLNOI的晶格常數(shù)(cr)是13.8604 A,小于體材料LN的13.8655A,向近化學(xué)計(jì)量比LN的13.8562A靠近。共聚焦微區(qū)拉曼散射對于LiNbO3晶格結(jié)構(gòu)的微小變化都很敏感,通過實(shí)驗(yàn)測得NSLNOI和LNOI在共聚焦微區(qū)拉曼散射下的散射峰,其中一部分峰的相對強(qiáng)度明顯降低,半高寬(FWHM)也有變化。
[Abstract]:From the end of twentieth Century began to integrated optics has been rapid development, it can achieve a plurality of optical components are integrated on the same chip material, forming a complex structure, powerful micro / small devices, to achieve one or more optical functions in communication / sensing, signal transmission, environmental monitoring and other fields have a wide range of applications. Integrated optics plays an irreplaceable role in modern optical communication and optical information processing applications, while the film is an integrated optical system, a key component. Single crystal materials with different optical properties together to form thin film materials through a certain way, can achieve a single crystal can the realization of the function. The lithium niobate (LiNbO3, LN) crystal is a kind of integrated optical crystal materials most widely used, because its have many excellent optical properties, such as piezoelectric, ferroelectric, optical, photoelastic, heat release Electric, photorefractive and nonlinear optical properties of.LN crystal optical silicon that became one of the few Jingjiubushuai, Everfount optical functional materials, open up new areas of application. In recent years, the emergence of a manufacturing method of high refractive index films. Ion implantation technology and crystal bonding technology the combination of the single crystal Lithium Niobate Thin film bonded to the deposition of SiO2 (also other materials) of the insulator substrate prepared by single crystal Lithium Niobate Thin Film (lithium niobate on insulator, LNOI). The LNOI material in this paper is a sandwich structure: /SiO2 layer LN film /LN substrate. The top layer is LN film thickness is about 0.5 m, the middle layer is amorphous SiO2, thickness of about 2 m, and the bottom layer is a high refractive index and LN substrate.LN film and SiO2 layer formation rate difference of light form limitations. Light is confined in a very small space, in a The low incident energy, LNOI produced waveguide light energy density can reach some optical properties of different.LN materials is very high in, such as nonlinear optical effect and electro-optic effect,.LNOI can be enhanced to some extent as an ideal platform for the production of integrated optical devices in LNOI, the performance of optical devices production may be greatly improved, so far there have been a lot of production on the LNOI devices is reported. But the performance device performance depends largely on the material, we know not much about LNOI optical and structural properties reported. Therefore, the structural and optical properties of LNOI should be further, for the design, preparation and evaluation of integrated optical devices on the LNOI help and promote the use of the core technology of.LNOI sample preparation is ion implantation ion beam through the light. Study of crystal in the application there are still some difficulties and challenges, research on the physical properties of materials by ion implantation and the lack of knowledge is one of the main reasons to limit the application of LNOI, which because of the nature of defects and damage caused by ion implantation is essential. Generally during ion implantation, injected electrons and lattice atoms ion and target the collision interaction, with a certain degree of damage to the crystal lattice structure. Damage will reduce the electro-optic coefficients of LN ion implantation, two order nonlinear coefficient of optical properties. The research of the crystal structure of LNOI, LNOI and parallel to the direction perpendicular to the direction of the measurement of stress and LN thin film layer and the substrate layer on the crystal face orientation difference, the prism coupling technique to measure the linear electro-optic coefficient gamma 13 and gamma 33 based on LNOI prepared by micro ring resonator, is proposed in Chemistry Stoichiometric method of preparation of LN film. The main contents and results are as follows: 1.LNOI lattice structure in the fabrication of LNOI during ion implantation process can lead to lattice damage, in this paper we through annealing in oxygen atmosphere to restore the lattice structure. Using the prism coupling technique experiment, Rutherford backscattering / channel technology, confocal micro Raman scattering and high resolution transmission electron microscopy to study the lattice damage of LNOI under different annealing conditions, the lattice structure with high resolution X ray evaluation LNOI. Experimental results show that the oxygen environment under 520 DEG C for 5 hours after the annealing of ion implantation damage birefringence recovery.LNOI much closer to the body material; channel spectrum display in the near surface LNOI is a perfect crystal; Raman spectra of LNOI and LN in the display materials are almost identical; TEM cross Cross section is displayed in the LiNbO3 film /Si02 layer interface is only a very thin layer of amorphous transition layer, the clear lattice fringes; no amorphous ring electron diffraction diagram, and the diffraction pattern is hexagonal pattern, high resolution X ray showed that.2.LNOI stress on many factors affecting the film the materials in LNOI good lattice, stress is an important factor that can not be ignored. The presence of stress will directly affect the stability and reliability of thin film materials, severe cases may cause the shedding of.LNOI thin film structure although only a few hundred nanometers in thickness, but the presence of stress can lead to distortions the interface lattice, thus affecting the optical properties and electrical properties of the films, the research damage may induce unpredictable stress influences the performance of.LNOI for the preparation of non ordinary optical devices Important. High resolution X ray (HRXRD) stress Omega -20 scanning can be used to characterize the LNOI parallel and vertical direction, because when X-ray characterization is lossless, and images with high accuracy and strong penetration of.HRXRD obtained from the LN film layer provides a way to directly measure the thin film strain component the change of Bo Mofeng's position. According to the calculated lattice constant and lattice constant characterization of stress, including the vertical pressure and parallel to the direction of the tensile force.HRXRD Phi scans can also be measured in a plane orientation LN thin film layer and the substrate during the process of alignment in key difference (delta phi). Due to the LN film the SiO2 layer and thermal expansion coefficient of different strain components formed LN film in vertical and horizontal directions. Experimental results show that, due to the thermal expansion coefficient of LN films is greater than Si02, the direction of the lattice constant level after annealing a, large vertical The direction of smaller Cr.HRXRD with scanning probe in (104) LN film layer and the substrate misorientation of LN crystal is 0.98 DEG 3.LNOI linear electro-optic coefficient has excellent electro-optical properties, with large electro-optic coefficient of linear (R 13=9.5 pm/V, gamma 33=31.2pm/V) based on the part of the.LN crystal as the integrated optical system. Is used to implement many optical devices, including acousto-optic devices, surface filter, electro-optical switch, electro-optical modulator. For LNOI, I hope LN film like material, also has a large electro-optic coefficient. The lattice damage caused by ion implantation, may affect the LN film layer. The electro-optic coefficient is improved a measurement method of planar waveguide electro-optic coefficients of the prism coupling technique based on the use of the prism coupling technique to measure the refractive index of LNOI, the upper and lower electrodes coupled with the electric field, and then measuring refractive index modulated by refractive index To determine the change of the linear electro-optic coefficients of LNOI. By using this method in the wavelength of incident light is 632.8 nm when measuring the electro-optic coefficient of 13 and 33. LNOI of gamma gamma results in oxygen atmosphere, the linear electro-optic coefficient gamma 520 C /5h annealed LNOI 13 and gamma 33 and LN bulk materials are to study.4. LNOI micro ring resonator in the LNOI above the preparation of optical devices, it will greatly improve the performance of optical nonlinear effect based on micro ring resonator by optical waveguide ring and straight waveguide coupled into the optical filter is a compact, integrated optical devices which can be used to build a variety of for different purposes, including light modulator, optical switch, optical add drop multiplexer, optical routers, optical sensors. The above in the LNOI design of the micro ring resonator. The sample is polished into a wedge, micro ring resonator etched in the wedge-shaped sample On the tip of the focused ion beam etching without changing the view, greatly improving the etching precision. We set up a coupling system of LNOI micro ring resonator and single-mode fiber. The test work related to micro ring resonator and straight waveguide coupling effect is.5. in the near stoichiometric LiNbO3 film preparation and characterization of LN the crystal is a kind of typical non stoichiometric 1:1 crystal, LN crystal has the same commercial component ratio ([Li]/[Nb]=48.4/51.6). The lack of lithium ions are caused by the large number of vacancy defects in the crystal, resulting in many physical properties of LN crystal can be affected by certain.LNOI from stripping down on LN crystals, components is no exception. LN crystal near-stoichiometric has emerged, some physical properties has been changed, such as reversal voltage decrease, double refraction difference increases. So it is necessary to produce high quality products LN near stoichiometric films, to explore the difference of refractive index, lattice constants and dipole moments of physical properties. The oxygen atmosphere annealing at 520 DEG C for 5 hours to improve the LNOI Li/Nb ratio of lithium rich vapor transport equilibration technique in this paper, the preparation of near stoichiometric lithium niobate thin film (NSLNOI). The use of measurement the refraction prism coupler, the laser wavelength of 632.8 nm is measured 2.1983 NSLNOI abnormal rate of light refraction, less than 2.2024 of the same component of LN, to the near stoichiometric LN 2.1898. Using the lattice constant measured by -20 scanning, NSLNOI high resolution X ray of the omega (CR) is 13.8604 A, less than the body LN 13.8655A, close to the stoichiometric ratio LN near 13.8562A. Confocal micro Raman scattering is very sensitive to small changes in the LiNbO3 lattice structure, scattering peak measured NSLNOI and LNOI in the confocal micro Raman scattering, a part of the peak The relative strength decreased obviously, and the half width (FWHM) also changed.

【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O484

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